If they rule for immunity, Biden should just hold Congress hostage until they pass some Constitutional amendments, such as scrapping Electoral College, adding term limits to Supreme Court, etc, then a final one that explicitly disavows any such immunity for the President or any other person, from the moment he releases them forward.
Velcro sewn to just inside the top of your pocket, so sticking a hand in your pocket makes a loud noise and you can feel it, for any pickpocket to separate the velcro.